hbswcsyzx opened a new pull request, #1884:
URL: https://github.com/apache/cloudberry/pull/1884
Fixes #1465
### What does this PR do?
Fixes a distributed snapshot visibility race during distributed transaction
commit. The coordinator now removes the distributed GXID from the proc array
before dispatching the QE commit notification. This prevents a concurrent
distributed snapshot from retaining a GXID after the QEs have committed the
transaction and incorrectly selecting the old tuple version.
The change retains the GXID/GID locally after proc-array cleanup so commit
retry, abort handling, diagnostics, and the `FORGET COMMITTED` record
continue
to use the correct transaction identifier. The same ordering is applied to
the one-phase commit notification path.
### Type of Change
- [x] Bug fix (non-breaking change)
- [ ] New feature (non-breaking change)
- [ ] Breaking change (fix or feature with breaking changes)
- [ ] Documentation update
### Test Plan
- [ ] Unit tests added/updated
- [x] Integration tests added/updated
- [ ] Passed `make installcheck`
- [ ] Passed `make -C src/test installcheck-cbdb-parallel`
Targeted validation for issue #1465 was performed in a fresh Docker cluster
built from this branch:
- The new isolation test reproduces the commit/proc-array race with fault
injection and passes with zero `gpdiff` output.
- The unpatched baseline deterministically returns the stale value; the fixed
build returns the committed value in both snapshot reads.
- `dtm_retry.sql` completes ten `COMMIT PREPARED` retries with a non-zero
GID,
and its abort-some-prepared and abort-prepared checks pass.
- One-phase commit success and injected QE failure/rollback paths pass.
- A 120-second targeted workload with 16 writers and 8 repeatable-read
readers completes successfully. The writers commit 6,692 transactions, the
final table sum is 6,692 with 1,000 rows, 46,207 reader transactions pass
their row-count assertions, and no prepared transactions remain.
- The final Docker cluster logs contain no `PANIC`, `FATAL`, or assertion
failure.
### Impact
**Performance:**
No additional network round trips are introduced. The coordinator performs
the existing proc-array cleanup before commit notification and retains the
transaction identifier locally for the remainder of the commit path.
**User-facing changes:**
This corrects snapshot visibility for concurrently committed distributed
updates. There are no syntax, catalog, or API changes.
**Dependencies:**
None.
### Checklist
- [x] Followed [contribution
guide](https://cloudberry.apache.org/contribute/code)
- [ ] Added/updated documentation
- [x] Reviewed code for security implications
- [ ] Requested review from [cloudberry
committers](https://github.com/orgs/apache/teams/cloudberry-committers)
### Additional Context
The fix is contained in `src/backend/cdb/cdbtm.c` and
`src/include/cdb/cdbtm.h`. The regression test is registered in the
isolation2
schedule at `src/test/isolation2/isolation2_schedule`.
The local Docker reproduction harness used for validation is intentionally
not
part of this PR.
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